doctype html
html
    head
        meta(charset='utf-8')
        title jade测试页面
        style.
            div{width:200px;height:200px;background:#ccc;line-height:200px;margin:10px auto;float:left}
            div.last{clear:left}
    body
        -var a = 0
        while a < 20
            if( a % 3 ==0 && a!=0 )
                div.last #{a++}
            else
                div=a++